The use of oligo(ribo)nucleotides and their analogues as anticancer and antiviruses theraupetic agents was first proposed several years ago. (Uhlmann, 1990) The great number of different modifications of the oligonucleotides and the methods of their use have since been developed.
Two basic interactions between oligonucleotides and nucleic acids are known (Moser and Dervan, 1987)    1. Watson-Crick base pairing (Duplex structure)    2. Hoogsten base pairing (Triplex structure)
Oligonucleotides can form duplex and/or triplex structures with DNA or RNA of cells and so regulate transcription or translation of genes.
It has been proposed that different substances which can cleave target nucleic acids or inhibit important cellular enzymes could be coupled to oligomers. The use of such conjugates as therapeutic agents has been described. (U.S. Pat. Nos. 5,177,198; 5,652,350).
Other methods are based on the coupling of different biologically active substances, such as toxins, to monoclonal antibodies which can then recognise receptors or other structures of cancer cells, or cells infected with viruses. Monoclonal antibodies can then specifically recognise cancer cells and in this way transport toxins to these cells. But these methods are inefficient due to the high level of nonspecific interactions between antibodies and other cells, which leads to delivary of the toxins or other biologically active compounds to the wrong cells.
In 1979 I. M. Klotz and co-authors proposed a method for complementary carrier peptide synthesis based on a template-directlyed scheme (J. A. Walder et al. 1979). The method proposed the synthesis of peptides on a solid support using unprotected amino acids, and the subsequent hybridization of oligonucleotides on the template. This method was established only for synthesis of peptides in vitro using solid supports of a different origin, and involved many synthesis steps to obtain peptides of the determined structure.
M. Masuko and co-authors proposed another method for in vitro detection of specific nucleic acids by excimer formation from two pyrene-labeled probes (Ebata, K. et al. 1995).
My invention allows the synthesis of different BACs of determined structure directly in living organisms only in cells which have specific RNA or DNA sequences. In this way, BACs will be delivered only to those cells where specific nucleic acids are produced.